Paste composition indicating water

Abstract

Visual indicating paste compositions are provided that are capable of producing a detectable color change upon contact with an aqueous liquid. The paste compositions include an indicator dye capable of changing color over a pH range of about 3 to about 11; an inorganic base capable of being converted to a more basic substance upon reaction with water; a liquid carrier (e.g., a polyalkylene glycol carrier); optionally, a gelling agent such as silica gel; and a proton donating compound such as a carboxylic acid or an organic sulfonic acid. When applied to a measuring probe, the paste compositions are particularly useful for detecting the level of water in the bottoms of tanks and delivery systems containing fuels such as gasoline by producing a clear, detectable color change upon contact with an aqueous liquid without bleeding or run-off. The paste compositions exhibit long shelf life and improved water resistance.

Description

Technical Field

[0001] This invention relates to stabilized visually indicative paste compositions and their use in detecting the presence, and particularly the level, of aqueous liquids when mixed with hydrocarbons such as gasoline, oil, or other fuels and petroleum fractions. More particularly, this invention relates to stabilized visually indicative paste compositions capable of undergoing a color change upon contact with aqueous liquids, which may be present in trace amounts (typically as a separate phase) in hydrocarbon storage tanks, transport vehicles, and distribution systems. The compositions of this invention are particularly suitable for use in determining the water level at the bottom of gasoline storage and transport tanks to ascertain the amount of water remaining in partially filled tanks containing hydrocarbons, and when the water contains oxygenated blending components such as ethers and alcohols. Background Technology

[0002] Paste compositions capable of detecting the presence or level (water level) of water have been disclosed in the prior art.

[0003] For example, U.S. Patent No. 4,699,885 discloses a visually indicative paste composition for producing a detectable color change upon contact with an aqueous liquid, comprising a water-soluble indicator dye capable of changing color in a pH range of about 7 to 11 and an insoluble inorganic base in the form of a caustic base powder dispersed in a liquid carrier capable of absorbing water but not being rapidly leached by water or hydrocarbon compounds. Chinese Publication Application No. CN103173206 discloses a similar paste composition. However, it has been found that the water-indicating pastes disclosed in these applications can discolor during storage due to the introduction of trace amounts of water from one or more sources. Therefore, water can permeate the paste if humid conditions exist during its manufacture or storage, or water can be absorbed by the paste each time the container is opened by a user for application. Furthermore, water can be introduced along with components used in the formulation of the paste, such as the liquid carrier.

[0004] U.S. Patent No. 4,717,671 describes a visually indicative paste composition similar to that disclosed in U.S. Patent No. 4,699,885, which achieves longer shelf life and improved water resistance by including a boron-containing compound (e.g., boron ester) in a moisture-inhibiting amount. This boron-containing compound is miscible with or soluble in a polyalkylene glycol carrier and is capable of hydrolyzing upon contact with water to form boric acid or its salts. The inventors report that attempts to replace such boron-containing compounds with other added organic compounds (including acids, anhydrides, salts, oxides, molecular sieve adsorbents, and active metal compounds) have been unsuccessful.

[0005] US Patent No. 6,376,250B1 describes incorporating aluminum isopropoxide as a water scavenger into a visually indicative paste composition comprising: a liquid carrier of a high molecular weight polyol, a caustic alkali powder selected from alkaline earth metal oxides, a gelling agent, a surfactant, a filler material, an indicator dye, and a neutral dye.

[0006] Despite the aforementioned progress, there remains a need for alternative methods to effectively stabilize water-indicating paste compositions to resist the harmful effects of small amounts of moisture that may come into contact with such paste compositions during their manufacture, storage, and / or repeated exposure to the ambient atmosphere due to the repeated opening of their storage containers over a period of time. Summary of the Invention

[0007] Embodiments of the present invention provide stabilized visual indicator pastes that exhibit extended shelf life and improved water resistance, while being characterized by low solubility in aqueous liquids and hydrocarbons, and good adhesion to substrates to which they are applied. Other aspects of the invention include methods for manufacturing such stabilized visual indicator pastes.

[0008] In other embodiments of the invention, a measuring probe coated with a stabilized visual indicator composition is provided, which can be used to locate the level of an aqueous liquid (e.g., a liquid containing water or water combined with oxygen-containing blending components such as alcohols and ethers) in the bottom of a hydrocarbon-containing tank and delivery system. A method for measuring the level of such an aqueous liquid within a container using such a probe is also provided.

[0009] It has now been found that paste compositions containing (i) an indicator dye capable of changing color in a pH range of about 3 to about 11, (ii) an inorganic base (typically dispersed in a liquid carrier based on one or more polyalkylene glycols), and (iii) optionally a gelling agent exhibit significant improvements in shelf life and water resistance compared to pastes without such proton-donating compounds, when such paste compositions contain relatively trace amounts of one or more proton-donating compounds having a pKa of no more than 12. This finding is surprising, especially considering the lessons learned from U.S. Patent No. 4,578,357, which attempted to stabilize similar paste compositions against the harmful effects of water using acids such as adipic acid and stearic acid without success. Detailed Implementation

[0010] According to the present invention, any proton-donating compound having a pKa of not more than 12, or a combination of such proton-donating compounds, can be used as a stabilizer in the paste compositions of the present invention. According to other embodiments, the pKa of the proton-donating compound is not greater than 11, not greater than 10, not greater than 9, or not greater than 8. In other embodiments, the pKa of the proton-donating compound may preferably be -3 or greater, -2 or greater, -1 or greater, or 0 or greater. For example, the pKa of the proton-donating compound may be in the range of -3 to 12, -2 to 10, or 0 to 8. If the proton-donating compound is capable of donating more than one proton (e.g., in the case of dicarboxylic acids such as citric acid), then the pKa used herein refers to the lowest pKa value, i.e., pKa1. The pKa of a compound is determined by conventional methods known in the art, and many different sources listing the pKa of known compounds are readily available.

[0011] In some other embodiments of the invention, it may be advantageous to provide that the proton compound or combination of such compounds is sufficiently miscible or soluble with the liquid carrier (e.g., polyalkylene glycol) component of the paste composition.

[0012] According to certain aspects of the invention, the proton-donating compound is at least partially water-soluble. However, preferably, the water solubility (water solubility) of the proton-donating compound is limited (i.e., the proton-donating compound is not freely soluble in water in all proportions). For example, the proton-donating compound may have a solubility in water at 25°C of at least 0.01 g / L or at least 0.05 g / L. In other examples, the proton-donating compound may have a solubility in water at 25°C of no more than 75 g / L or no more than 60 g / L.

[0013] The proton-donating compound is preferably an organic compound, such as an organic acid. Suitable acids for the purposes of this invention include, but are not limited to, carboxylic acids (organic compounds containing one or more -CO2H groups) and organic sulfonic acids (organic compounds containing one or more -SO3H groups). The organic acid can be an aliphatic organic acid (meaning that the acid functional group is substituted on an aliphatic carbon atom) or an aromatic organic acid (meaning that the acid functional group is substituted on an aromatic carbon atom). Organic acids containing one or more aliphatic moieties and one or more aromatic moieties can also be used.

[0014] Examples of suitable proton-donating compounds that may be used in this invention include, but are not limited to: C4-C24 aliphatic carboxylic acids, including C6-C24 aliphatic monocarboxylic acids (which may be saturated or unsaturated and may be linear or branched or may contain one or more aliphatic ring structures) and C4-C8 aliphatic dicarboxylic acids (which may be saturated or unsaturated and may be linear or branched); and C6-C18 alkylated arylsulfonic acids (i.e., compounds in which C6-C18 alkyl groups and sulfonic acid groups are attached to an aromatic ring such as a benzene ring); for example, nonanoic acid, dodecylbenzenesulfonic acid, adipic acid, succinic acid, and combinations thereof.

[0015] A proton-donating compound or combination of proton-donating compounds is used in the paste composition in an amount sufficient to provide the desired level of stabilization or moisture inhibition. Simultaneously, such an amount should not be large enough to interfere with the ability of the paste composition to detect color change in an aqueous liquid for the intended purpose and within the desired time period (typically, less than one minute after contact with such an aqueous liquid at 25°C). Therefore, according to some embodiments, the amount of the at least one proton-donating compound contained in the paste composition is effective in stabilizing the paste composition to resist color change when the paste composition is exposed to air with 70% relative humidity at 25°C for at least 10 minutes. In a further embodiment, the amount of the at least one proton-donating compound contained in the paste composition is effective in allowing the paste composition to exhibit a color change within 1 minute or 30 seconds of contact with pure water at 25°C. In some embodiments of the invention, the foregoing two criteria may be satisfied (i.e., the amount of the at least one proton-donating compound that may be included in the paste composition is effective for both: stabilizing the paste composition to resist color change when the paste composition is exposed to air with 70% relative humidity at 25°C for at least 10 minutes, and allowing the paste composition to exhibit color change within 1 minute or 30 seconds of contact with pure water at 25°C). Typically, based on the total weight of the paste composition, the proton-donating compound may be present in the paste composition of the invention at a concentration ranging from about 0.01% to about 5%. The amount of proton-donating compound (one or more) may be adjusted as appropriate based on the specific proton-donating compound (one or more) selected, the pKa value (one or more) of the proton-donating compound (one or more), the type and amount of inorganic base, and other factors.

[0016] According to some embodiments, the at least one first inorganic base and the at least one proton-donating compound are present in an effective amount such that a weight ratio of first inorganic base to proton-donating compound of 1:1 to 100:1 is provided. According to other embodiments, the at least one proton-donating compound is present in the paste composition in stoichiometric excess relative to the total amount of water and the second inorganic base present in the preparation of the paste composition.

[0017] The stabilized visual indicator paste composition of the present invention, upon contact with water or an aqueous liquid (i.e., an aqueous liquid, such as an aqueous oxidized hydrocarbon), typically changes color within about 60 seconds or less, or about 30 seconds or less, and generally within about 5 to 15 seconds or less, depending on the indicator dye used, at 25°C. The oxidized hydrocarbon can be selected from, for example, lower alcohols, illustratively methanol, ethanol, tert-butanol, sec-butanol, and mixtures thereof; lower polyols such as alkylene glycols; and lower ketones such as acetone, and methyl tert-butyl ether, etc. The term "aqueous liquid" is used herein to refer to a substance having chemical properties similar to those of water, as distinct from "oily liquid," i.e., fuels, petroleum, or hydrocarbon oils, etc., that do not cause color change in the compositions of the present invention. The aqueous liquids mentioned above may contain up to about 95% oxidized hydrocarbons and are typically obtained from an oxygenated blend used in hydrocarbons (e.g., gasoline) that leach from the hydrocarbons into the aqueous layer. According to some embodiments, an aqueous liquid is a homogeneous liquid or solution in which water is dissolved or solubilized in one or more non-aqueous components, such as an oxygen-containing blend, or in which one or more non-aqueous components are dissolved or solubilized in water.

[0018] The indicator dye used in the paste compositions of the present invention is preferably a water-soluble dye, readily available from commercial sources as a fine anhydrous crystalline powder. Typically, the dye particles exhibit a diameter of no more than about 200 micrometers. These dyes are characterized by their ability to cause a color change in the paste composition within a pH range of about 3 to about 11 when the paste composition is contacted with water. Typically, the initially formulated paste composition is characterized by having a first pH value and a first color resulting from the color of the indicator dye at the first pH value. When the paste composition is contacted with an aqueous liquid, the water present in the aqueous liquid is believed to interact with a first inorganic base (e.g., calcium oxide) present in the paste composition to form a second inorganic base (e.g., calcium hydroxide) that is more alkaline than the first inorganic base. The formation of the second inorganic base results in an increase in pH; that is, the paste composition exhibits a second pH value higher than the first pH value. The second pH value is sufficiently greater than the first pH value for the indicator dye to change color. For example, the indicator dye may be colorless at the first pH value but may be blue or purple at the second (higher) pH value.

[0019] Such indicator dyes are generally used as a component of the paste composition in an amount sufficient to provide the desired color change. Typically, such dyes can be used at a concentration ranging from about 0.05 to about 5%, preferably about 0.1 to about 3%, based on the total weight of the paste composition. Representative indicator dyes that can be used as components in the compositions of the present invention include, but are not limited to: phenolphthalein, o-cresolphthalein, p-naphthol benzyl alcohol, ethyl bis(2,4-dinitrophenol), thymolphthalein, Nile Blue A, cresol red, bromophenol blue, and thymol blue. The indicator dyes used may be selected based on their control status and / or their toxicity characteristics.

[0020] The inorganic base used as a component of the visual indicator paste composition of the present invention must be such that it does not dissolve and ionize in a liquid carrier to any significant extent, but is readily soluble in water (directly, or, as in the case of calcium oxide (which reacts with water to form calcium hydroxide), is readily soluble in water due to its reaction with water). According to embodiments of the invention, the inorganic base is present in the paste composition in the form of fine particles, for example, as a powder. According to some embodiments of the invention, the fine particles of the inorganic base may be dispersed in a liquid carrier. Generally, anhydrous solid forms of alkaline earth metal oxides, hydroxides, or mixtures thereof, or any compound that would produce alkaline earth metal oxides or hydroxides in situ (e.g., alkaline earth metal hydrides) are suitable for use in the paste compositions of the present invention. These materials may be in the form of finely crystalline industrial-grade powders and are readily available from commercial sources. Typical inorganic bases that may be used according to the invention include calcium oxide, calcium hydroxide, strontium oxide, strontium hydroxide, barium oxide, barium hydroxide, magnesium oxide, magnesium hydroxide, and hydrides of these metals, such as calcium hydride. Alkaline earth metal oxides, such as calcium oxide (CaO), are particularly suitable for use in this invention.

[0021] The choice of inorganic base will depend in part on the specific indicator dye or combination of indicator dyes used to formulate the paste composition. For example, an inorganic base may be chosen such that it imparts a pH to the paste composition as initially formulated, at which the indicator dye also present in the paste composition is of the first color (or colorless).

[0022] Typically, inorganic bases are used at concentrations ranging from about 1% to about 25% of the paste composition by weight, preferably from about 5% to about 20%, to provide the desired water-sensitive properties of the paste compositions of the present invention.

[0023] As a carrier for the paste compositions of the present invention, a liquid carrier is used that is capable of absorbing water but is not readily leached by water or by hydrocarbons that the paste composition will come into contact with during its intended use. In this context, the term "liquid carrier" refers to a carrier that is liquid at 25°C. Any organic compound or mixture thereof that exhibits inertness to other compositional components may be used. Other desirable liquid carrier characteristics include a viscosity sufficiently high for good paste consistency, a low freezing point, and no inhibition of the relatively rapid color reaction of the indicator dye (i.e., within about 2 minutes or less after the paste composition comes into contact with an aqueous liquid). Particularly suitable liquid carriers include aliphatic polyols, alkylene glycols, and polyalkylene glycols with sufficiently high molecular weights to exclude their solubility in the aqueous / hydrocarbon environment of the visually indicative paste composition. Typically, polyols, glycols, and mixtures thereof having a number average molecular weight of at least about 75 g / mol can be used as liquid carriers in the compositions of the present invention. Illustrative polyols that can be used in the compositions of the present invention include 1,4-butanediol; 1,3-butanediol; hexylene glycol; 1,2,6-hexanetriol; and 1,6-hexanediol. Polyalkylene glycols generally contain about 2-4 carbon atoms in each alkylene chain unit (e.g., the alkylene chain unit may be oxyethylene, oxypropylene, and / or oxybutylene chain units). Illustrative polyalkylene glycols that can be used include polyethylene glycol, polypropylene glycol, polyethylene glycol / propylene glycol (random or block), and polybutanediol having a number-average molecular weight (e.g., determined by gel permeation chromatography) of about 200-4000 g / mol. As will be apparent to those skilled in the art, such polyols and glycols are commercially available products and can be used alone or as mixtures with or without other conventional liquid carriers, and when used as mixtures, they are used to obtain an optimal hydrophilic / hydrophobic balance. In some embodiments of the invention, combinations or mixtures of polypropylene glycol and polyethylene glycol are used. Typically, the liquid carrier is used in an amount of at least about 40% by weight, and typically about 50% to about 90% by weight, based on the total weight of the paste composition. Polyalkylene glycols (particularly polyethylene glycol and polypropylene glycol, including combinations thereof) with a number average molecular weight of about 200-1500 g / mol, used in an amount of about 60-80% of the total weight of the paste composition, provide particularly desirable properties and are therefore preferred for use in the compositions of the invention.

[0024] If desired, a gelling agent or combination of gelling agents that acts as a thickener and / or color stabilizer and is inert to other components of the paste composition may optionally be used as an additive to the paste composition of the present invention. The purpose of using such a gelling agent is to delay leaching and gel the composition. Any known substance that has a color other than that which would interfere with the visual detection provided by the paste composition of the present invention in its application, and which is used to provide the indicated thickening properties and color stabilization, may be used. Illustrative suitable gelling agents used as components of the paste composition of the present invention include inert inorganic fillers or diluents, such as talc, clay, diatomaceous earth, calcium silicate, silica, pyrolytic colloidal silica, alumina, pyrophyllite, calcite, or mixtures thereof, or other finely crushed solid materials. Typically, if used, the gelling agent is used in an amount up to about 20% by weight or more, or preferably about 2% to about 15% by weight, based on the total weight of the paste composition.

[0025] The compositions of the present invention can be prepared by conventional methods in the art for producing paste compositions. Typically, the components of the composition are fed into a mixer at ambient temperature and blended into a homogeneous, smooth paste. It should be understood that blending at elevated temperatures or under other conditions conventionally used for blending pastes can also be used. The introduction of the composition components is readily achieved by introducing the components individually or together into a liquid carrier via grinding, dry mixing, or blending. Therefore, inorganic bases, indicator dyes, proton-donating compounds, and / or gelling agents (if used) can be introduced before, simultaneously with, or after the introduction of other components into the liquid carrier. Alternatively, the proton-donating compound can be dissolved in the liquid carrier before the solid components are introduced.

[0026] According to a preferred embodiment, the paste composition can be prepared by a method comprising the following steps:

[0027] a) At least one indicator dye that is capable of changing color in a pH range of about 3 to about 11;

[0028] b) At least one inorganic base that can react with water to convert a first inorganic base into a second inorganic base that is more basic than the first inorganic base;

[0029] c) At least one liquid carrier;

[0030] d) Optionally, at least one gelling agent; and

[0031] e) At least one proton-donating compound having a pKa of up to 12, preferably up to 10, and more preferably up to 8.

[0032] Specifically, such a method may include the following steps:

[0033] a) Combining at least one liquid carrier, at least one indicator dye, and at least one proton-donating compound to obtain a first mixture;

[0034] b) Combining the first mixture with at least one inorganic base to obtain a second mixture; and

[0035] c) Optionally (but preferably), the second mixture is combined with at least one gelling agent to obtain a paste composition.

[0036] Water is advantageously removed during the preparation of the paste composition. For example, the components of the paste composition may be anhydrous or substantially anhydrous. According to some embodiments of the invention, certain components of the paste composition may be combined and dried to remove water or reduce water content before the addition of other components of the paste composition. For example, if multiple liquid carriers, such as different polyalkylene glycols, are used in the formulation of the paste composition, such liquid carriers may be combined and vacuum stripped while heating to reduce water content, and then the remaining components (with a satisfactory low water content) may be added. The combination of components of the paste composition may be done under a dry atmosphere (e.g., dry nitrogen) to prevent atmospheric water from being absorbed into the paste composition. Once the paste composition according to the invention has been formulated, it may be transferred to a suitable sealable container that can be easily opened to allow dispensing of the paste composition and then resealed to protect the previous composition from moisture exposure. Suitable sealable containers include, for example, capped tubes, bottles, barrels, and drums made of suitable materials such as plastic or metal.

[0037] It should be understood that the paste composition of the present invention may further include additives well known to those skilled in the art, such as adhesives, water-removing agents, etc. As an adhesive, materials such as casing gelatin, cellulose derivatives such as carboxymethyl cellulose, sulfite waste liquid, water-dispersible synthetic resins, mineral oils, or equivalent adhesives may be used, all of which are well known in the art.

[0038] The paste compositions of the present invention may additionally contain one or more surfactants, such as nonionic surfactants (e.g., ethoxylated nonylphenol surfactants), typically up to about 5% by weight (e.g., 0.1%-4% by weight) based on the total weight of the paste composition.

[0039] One or more fillers other than gelling agents may also be present in the paste composition. Calcium carbonate and gypsum are examples of suitable fillers.

[0040] This invention provides readily usable stabilized paste compositions, particularly suitable for locating water levels in tanks or other storage or transport facilities for hydrocarbons that are miscible with water or with "aqueous liquids" as defined above. One particular application of the paste compositions of this invention is found to be measuring the level of bottom water in gasoline storage tanks that must be frequently monitored to prevent water from entering vehicle gasoline tanks. Bottom water in storage or transport facilities containing oxygenated blends (i.e., gasoline containing alcohols or ethers such as methanol, ethanol, tert-butanol, methyl tert-butyl ether, or mixtures thereof) may contain up to about 90% by volume of alcohol.

[0041] The paste composition according to the invention can be used to measure the level of aqueous liquid present in a container. Typically, if a hydrocarbon fuel, such as gasoline, has become contaminated with excessive water, phase separation is observed in the contents of a container, such as a can, used to store or contain the hydrocarbon fuel, wherein an aqueous liquid phase forms at the bottom of the container and a hydrocarbon phase (with a lower density than the aqueous liquid phase) forms as a separate phase on top of the aqueous liquid phase. A certain amount of the paste composition according to the invention can be placed as a layer (preferably a thin, uniform layer) on at least one end of a measuring probe. The measuring probe can be elongated and sized to reach the bottom of the container when assembled through an opening at the top of the container. The measuring probe can be made of any suitable material resistant to the contents of the container, such as wood, metal, or engineering thermoplastics. One end of the measuring probe on which the layer of paste composition is disposed can then extend downward through the container opening and the contents of the container until it reaches the bottom of the container. If the paste composition comes into contact with an aqueous liquid, a measuring probe is held in contact with the container contents for a period of time (typically up to 1 or 2 minutes) effective for achieving a color change in the paste composition. The container is then removed and any color change is visually inspected. Because the paste composition only visibly changes color upon contact with water in an aqueous liquid form, the presence and depth of any aqueous phase that has formed in the container can be easily determined. If such an aqueous phase is detected, remedial actions can then be taken, such as siphoning out the aqueous phase or emptying and cleaning the container.

[0042] The illustrative and non-limiting aspects of this invention can be summarized below:

[0043] Aspect 1: A paste composition for producing a detectable color change upon contact with an aqueous liquid, comprising:

[0044] a) At least one indicator dye that is capable of changing color in a pH range of about 3 to about 11;

[0045] b) At least one first inorganic base, which is capable of reacting with water to convert the first inorganic base into a second inorganic base that is more basic than the first inorganic base;

[0046] c) At least one liquid carrier;

[0047] d) Optionally, at least one gelling agent; and

[0048] e) At least one proton-donating compound having a pKa of up to 12, preferably up to 10, and more preferably up to 8.

[0049] Aspect 2: The paste composition of aspect 1, wherein the at least one proton-donating compound comprises at least one organic acid.

[0050] Aspect 3: A paste composition of aspect 1 or 2, wherein the at least one proton-donating compound comprises at least one organic acid selected from carboxylic acids, organic sulfonic acids, and combinations thereof.

[0051] Aspect 4: A paste composition of any one of Aspects 1-3, wherein the at least one proton-donating compound comprises at least one organic acid selected from the group consisting of C6-C24 aliphatic carboxylic acids, C6-C18 alkylated aryl sulfonic acids, and combinations thereof.

[0052] Aspect 5: A paste composition of any one of Aspects 1-4, wherein the at least one proton-donating compound comprises at least one organic acid selected from nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

[0053] Aspect 6: A paste composition of any one of Aspects 1-5, wherein the at least proton-donating compound comprises at least one proton-donating compound having a solubility in water at 25°C of 0.01 g / L to 75 g / L.

[0054] Aspect 7: A paste composition of any one of Aspects 1-6, wherein the at least one proton-donating compound has a pKa of at least 0.

[0055] Aspect 8: A paste composition of any one of Aspects 1-7, wherein the at least one proton-donating compound is present in stoichiometric excess relative to the total amount of water and the second inorganic base present in the preparation of the paste composition.

[0056] Aspect 9: The paste composition of any one of Aspects 1-8, wherein the amount of the at least one proton-donating compound contained therein is effective for stabilizing the paste composition to resist color change when the paste composition is exposed at 25°C to air having a relative humidity of 70% for at least 10 minutes.

[0057] Aspect 10: A paste composition of any one of Aspects 1-9, wherein the amount of the at least one proton-donating compound contained therein is effective for allowing the paste composition to exhibit a color change at 25°C within 1 minute of contact with water.

[0058] Aspect 11: A paste composition of any one of Aspects 1-10, comprising a total of about 0.01 to about 5% by weight of the at least one proton-donating compound.

[0059] Aspect 12: A paste composition of any one of Aspects 1-11, wherein the at least one first inorganic base and the at least one proton-donating compound are present in an amount effective to provide a weight ratio of 1:1 to 100:1 for the first inorganic base to the proton-donating compound.

[0060] Aspect 13: A paste composition of any one of Aspects 1-12, wherein the at least one indicator dye comprises at least one water-soluble indicator dye.

[0061] Aspect 14: A paste composition of any one of Aspects 1-13, wherein the at least one indicator dye comprises at least one indicator dye selected from the group consisting of o-cresolphthalein, phenolphthalein, p-naphthol benzyl alcohol, ethyl bis(2,4-dinitrophenol), thymolphthalein, Nile Blue A, cresol red, bromophenol blue, and thymol blue.

[0062] Aspect 15: A paste composition of any one of Aspects 1-14, wherein the at least one first inorganic base comprises CaO.

[0063] Aspect 16: A paste composition of any one of Aspects 1-15, wherein the at least one liquid carrier comprises at least one polyalkylene glycol.

[0064] Aspect 17: A method for preparing a paste composition for producing a detectable color change upon contact with an aqueous liquid, comprising:

[0065] a) At least one indicator dye that is capable of changing color in a pH range of about 3 to about 11;

[0066] b) At least one inorganic base that can react with water to convert a first inorganic base into a second inorganic base that is more basic than the first inorganic base;

[0067] c) At least one liquid carrier;

[0068] d) Optionally, at least one gelling agent; and

[0069] e) At least one proton-donating compound having a pKa of up to 12, preferably up to 10, and more preferably up to 8.

[0070] Aspect 18: The method of aspect 17 includes the following steps:

[0071] a) Combining the at least one polyalkylene glycol, the at least one indicator dye, and the at least one proton-donating compound to obtain a first mixture;

[0072] b) Combining the first mixture with the at least one inorganic base to obtain a second mixture; and

[0073] c) Optionally, the second mixture is combined with the at least one gelling agent to obtain a paste composition.

[0074] Aspect 19: The method of aspect 17 or 18, wherein the at least one proton-donating compound comprises at least one organic acid.

[0075] Aspect 20: The method of any one of Aspects 17-19, wherein the at least one proton-donating compound comprises at least one organic acid selected from carboxylic acids, organic sulfonic acids, and combinations thereof.

[0076] Aspect 21: The method of any one of Aspects 17-20, wherein the at least one proton-donating compound comprises at least one organic acid selected from: C6-C24 aliphatic carboxylic acids, C6-C18 alkylated aryl sulfonic acids, and combinations thereof.

[0077] Aspect 22: The method of any one of Aspects 17-21, wherein the at least one proton-donating compound comprises at least one organic acid selected from nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

[0078] Aspect 23: The method of any one of Aspects 17-22, wherein the at least proton-donating compound comprises at least one proton-donating compound having a solubility in water at 25°C of 0.01 g / L to 75 g / L.

[0079] Aspect 24: The method of any one of Aspects 17-23, wherein the at least one proton-donating compound has a pKa of at least 0.

[0080] Aspect 25: The method of any one of Aspects 17-24, wherein the amount of the at least one proton-donating compound used is stoichiometric excess relative to the total amount of water and the second inorganic base present in the preparation of the paste composition.

[0081] Aspect 26: The method of any one of Aspects 17-25, wherein the amount of the at least one proton-donating compound used is effective for stabilizing the paste composition to resist color change when the paste composition is exposed at 25°C to air having a relative humidity of 70% for at least 10 minutes.

[0082] Aspect 27: The method of any one of Aspects 17-26, wherein the amount of the at least one proton-donating compound used is effective for allowing the paste composition to exhibit a color change at 25°C within 1 minute of contact with water.

[0083] Aspect 28: The method of any one of Aspects 17-27, wherein the paste composition comprises a total of about 0.01 to about 2% by weight of the at least one proton-donating compound.

[0084] Aspect 29: The method of any one of Aspects 17-28, wherein the at least one indicator dye comprises at least one water-soluble indicator dye.

[0085] Aspect 30: The method of any one of Aspects 17-29, wherein the at least one indicator dye comprises at least one indicator dye selected from the group consisting of o-cresolphthalein, phenolphthalein, p-naphthol benzyl alcohol, ethyl bis(2,4-dinitrophenol), thymolphthalein, Nile Blue A, cresol red, bromophenol blue, and thymol blue.

[0086] Aspect 31: A paste composition obtained by any one of aspects 18-30.

[0087] Aspect 32: A method for detecting an aqueous liquid in a container having contents thereon, wherein the method comprises contacting a measuring probe having a layer of a paste composition according to any one of aspects 1-16 or 31 thereon with the contents of the container, removing the measuring probe from the container, and visually inspecting the color change of the layer of paste composition caused by the interaction between the paste composition and the aqueous liquid.

[0088] Example

[0089] Example 1:

[0090] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 2.0 g of o-cresolphthalein and 1.0 g of dodecylbenzenesulfonic acid. Stir at 65°C until the solids dissolve. Add 7.0 g of calcium oxide and disperse. Slowly add 6.0 g of... M5 pyrolyzes silica and stirs to form a paste. The paste is grayish-white. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns light purple within 2 seconds and dark purple within 15 seconds.

[0091] Example 2:

[0092] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 0.425 g of thymol blue and 0.085 g of nonanoic acid. Stir at 65°C until the solids dissolve. Add 7.0 g of calcium oxide and disperse. Slowly add 8.0 g of... M5 pyrolyzes silica and stirs to form a paste. This paste is orange. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns pale blue within 12 seconds and dark blue within 25 seconds. Although the paste stored in sealed sample containers turns green within 30 days, a much longer shelf life is expected when such compositions are prepared on a larger commercial scale under more stringent moisture-removing conditions.

[0093] Example 3:

[0094] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 0.5 g of thymol blue and 0.44 g of adipic acid. Stir at 65°C until the solid dissolves. Add 7.0 g of calcium oxide and disperse. Slowly add 6.0 g of... M5 pyrolyzes silica and stirs to form a paste. The paste is orange. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns pale blue within 2 seconds.

[0095] Example 4:

[0096] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 0.5 g of thymol blue and 0.36 g of succinic acid. Stir at 65°C until the solids dissolve. Add 7.0 g of calcium oxide and disperse. Slowly add 6.0 g of... M5 pyrolyzes silica and stirs to form a paste. The paste is orange. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns pale blue within 2 seconds.

[0097] Example 5:

[0098] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 1.0 g of thymolphthalein and 1.0 g of dodecylbenzenesulfonic acid. Stir at 65°C until the solids dissolve. Add 7.0 g of calcium oxide and disperse. Slowly add 6.0 g of... M5 pyrolyzes silica and stirs to form a paste. The paste is grayish-white. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns light blue within 15 seconds and dark blue within 60 seconds.

[0099] Example 6:

[0100] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 0.25 g of cresol red and 2.0 g of dodecylbenzenesulfonic acid. Stir at 65°C until the solids dissolve. Add 7.0 g of calcium oxide and disperse. Slowly add 6.0 g of... M5 pyrolyzes silica and stirs to form a paste. The paste is brown. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns light purple within 5 seconds and dark purple within 15 seconds.

[0101] Example 7:

[0102] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 0.2 g of bromophenol blue and 5.0 g of dodecylbenzenesulfonic acid. Stir at 65°C until the solid dissolves. Add 7.0 g of calcium oxide and disperse. Slowly add 6.0 g of... M5 pyrolyzes silica and stirs to form a paste. The paste is brown. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns light blue within 2 seconds and dark blue within 10 seconds.

[0103] Example 8 (Comparative):

[0104] Add 26.5 g of polypropylene glycol (molecular weight = 750 g / mol), 26.5 g of polypropylene glycol (molecular weight = 1025 g / mol), and 31.6 g of polyethylene glycol (molecular weight = 400 g / mol) to a round-bottom flask equipped with a stirrer, heating mantle, and temperature controller. Purge with nitrogen and apply vacuum. Heat to 65°C and apply full vacuum to reduce the water content to <300 ppm. Stop the vacuum and add 0.86 g of thymol blue and 0.085 g of tripropyl borate. Stir at 65°C until the solids dissolve. Add 7.0 g of calcium oxide and disperse. Slowly add 8.0 g of... M5 pyrolyzes silica and stirs to form a paste. This paste is deep orange. When applied to a wooden stick and immersed in E10 gasoline containing 1 phr of water, the paste in contact with the water layer turns light blue within 10 seconds and dark blue within 20 seconds, and black spots form on the paste where it contacts the hydrocarbon layer above the water layer. The paste in a sealed sample container turns blue within one day.

[0105] This embodiment demonstrates the beneficial effects of including a proton-donating compound in the paste composition according to the invention. The paste composition of Example 8 contains tripropyl borate (a stabilizer taught in the prior art) but does not contain a proton-donating compound. A much shorter shelf life was observed compared to the paste composition of Example 2, which has a composition similar to that of Example 8, except that it contains nonanoic acid instead of tripropyl borate.

Claims

1. A paste composition for producing a detectable color change upon contact with an aqueous liquid, comprising: a) At least one indicator dye that can change color in a pH range of 3 to 11; b) At least one first inorganic base, which is capable of reacting with water to convert the first inorganic base into a second inorganic base that is more basic than the first inorganic base; c) At least one liquid carrier; d) Optionally, at least one gelling agent; and e) at least one proton-donating compound having a pKa of up to 12, wherein the at least one proton-donating compound comprises at least one organic acid selected from the group consisting of C6-C24 aliphatic carboxylic acids, C6-C18 alkylated aryl sulfonic acids, and combinations thereof. The paste composition comprises a total of 0.01-5% by weight of the at least one proton-donating compound, and wherein the at least one first inorganic base and the at least one proton-donating compound are present in an effective amount of providing a first inorganic base to proton-donating compound weight ratio of 1:1 to 100:

1.

2. The paste composition according to claim 1, wherein the at least one proton-donating compound has a pKa of up to 10.

3. The paste composition according to claim 2, wherein the at least one proton-donating compound has a pKa of up to 8.

4. The paste composition according to any one of claims 1 to 3, wherein the at least one proton-donating compound comprises at least one organic acid selected from nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

5. The paste composition according to any one of claims 1 to 3, wherein the at least proton-donating compound comprises at least one proton-donating compound having a solubility in water at 25°C of 0.01 g / L to 75 g / L.

6. The paste composition according to any one of claims 1 to 3, wherein the at least one proton-donating compound has a pKa of at least 0.

7. The paste composition according to any one of claims 1 to 3, wherein the at least one proton-donating compound is present in stoichiometric excess relative to the total amount of water and the second inorganic base present in the preparation of the paste composition.

8. The paste composition according to any one of claims 1 to 3, wherein the amount of the at least one proton-donating compound contained therein is effective for stabilizing the paste composition to resist color change when the paste composition is exposed at 25°C to air with 70% relative humidity for at least 10 minutes.

9. The paste composition according to any one of claims 1 to 3, wherein the amount of the at least one proton-donating compound contained therein is effective in allowing the paste composition to exhibit a color change at 25°C within 1 minute of contact with water.

10. The paste composition according to any one of claims 1 to 3, wherein the at least one indicator dye comprises at least one water-soluble indicator dye.

11. The paste composition according to any one of claims 1 to 3, wherein the at least one indicator dye comprises at least one indicator dye selected from the group consisting of: o-cresolphthalein, phenolphthalein, p-naphthol benzyl alcohol, ethyl bis(2,4-dinitrophenol), thymolphthalein, Nile Blue A, cresol red, bromophenol blue, and thymol blue.

12. The paste composition according to any one of claims 1 to 3, wherein the at least one first inorganic base comprises CaO.

13. The paste composition according to any one of claims 1 to 3, wherein the at least one liquid carrier comprises at least one polyalkylene glycol.

14. A method for preparing a paste composition for producing a detectable color change upon contact with an aqueous liquid, comprising: a) At least one indicator dye that can change color in a pH range of 3 to 11; b) At least one inorganic base that can react with water to convert a first inorganic base into a second inorganic base that is more basic than the first inorganic base; c) At least one liquid carrier; d) Optionally, at least one gelling agent; and e) at least one proton-donating compound having a pKa of up to 12, wherein the at least one proton-donating compound comprises at least one organic acid selected from the group consisting of C6-C24 aliphatic carboxylic acids, C6-C18 alkylated aryl sulfonic acids, and combinations thereof. The paste composition comprises a total of 0.01-5% by weight of the at least one proton-donating compound, and wherein the at least one first inorganic base and the at least one proton-donating compound are present in an effective amount of providing a first inorganic base to proton-donating compound weight ratio of 1:1 to 100:

1.

15. The method of claim 14, wherein the at least one proton-donating compound has a pKa of up to 10.

16. The method of claim 15, wherein the at least one proton-donating compound has a pKa of up to 8.

17. The method of claim 14, further comprising the following steps: a) Combining the at least one polyalkylene glycol, the at least one indicator dye, and the at least one proton-donating compound to obtain a first mixture; b) Combining the first mixture with the at least one inorganic base to obtain a second mixture; and c) Optionally, the second mixture is combined with the at least one gelling agent to obtain a paste composition.

18. The method according to any one of claims 14 to 17, wherein the at least one proton-donating compound comprises at least one organic acid selected from nonanoic acid, dodecylbenzenesulfonic acid, and combinations thereof.

19. The method according to any one of claims 14 to 17, wherein the at least proton-donating compound comprises at least one proton-donating compound having a solubility in water at 25°C of 0.01 g / L to 75 g / L.

20. The method according to any one of claims 14 to 17, wherein the at least one proton-donating compound has a pKa of at least 0.

21. The method according to any one of claims 14 to 17, wherein the amount of the at least one proton-donating compound used is stoichiometric excess relative to the total amount of water and the second inorganic base present in the preparation of the paste composition.

22. The method according to any one of claims 14 to 17, wherein the amount of the at least one proton-donating compound used is effective for stabilizing the paste composition to resist color change when the paste composition is exposed at 25°C to air with 70% relative humidity for at least 10 minutes.

23. The method according to any one of claims 14 to 17, wherein the amount of the at least one proton-donating compound used is effective in allowing the paste composition to exhibit a color change within 1 minute of contact with water at 25°C.

24. The method according to any one of claims 14 to 17, wherein the paste composition comprises a total of 0.01-2% by weight of the at least one proton-donating compound.

25. The method according to any one of claims 14 to 17, wherein the at least one indicator dye comprises at least one water-soluble indicator dye.

26. The method according to any one of claims 14 to 17, wherein the at least one indicator dye comprises at least one indicator dye selected from the group consisting of o-cresolphthalein, phenolphthalein, p-naphthol benzyl alcohol, ethyl bis(2,4-dinitrophenol), thymolphthalein, Nile Blue A, cresol red, bromophenol blue, and thymol blue.

27. A method for detecting an aqueous liquid in a container having contents therein, wherein the method comprises contacting a measuring probe having a layer of a paste composition according to any one of claims 1 to 13 disposed thereon with the contents of the container, removing the measuring probe from the container, and visually inspecting the color change of the layer of the paste composition caused by the interaction between the paste composition and the aqueous liquid.